FIG. 12 is a cross sectional view that shows essential portions of a known fuel injection valve.
In this known fuel injection valve, a ball 13 at a tip end of a valve element is moved apart from a valve seat 10, whereby fuel is injected from a plurality of injection holes 12A in an injection hole plate 11A bonded to a lower end face of the valve seat 10 into an intake pipe of an engine.
This injection hole plate 11A is formed at its central portion with a convex portion 11d of a circular-arc shaped cross section which is substantially axisymmetric with respect to a valve seat axis 10c, and which protrudes to a downstream side, and the plurality of injection holes 12A are formed through the convex portion 11d (see, for example, a first and a second patent document).
[First Patent Document]
Japanese patent application laid-open No. 2001-27169
[Second Patent Document]
Japanese patent application laid-open No. 2006-207419